The Ins and Outs of Solid-State Storage

Experts say SSDs are heading for your data center. And they're right. They are also quick to point out that SSDs will not take over completely-that there will still be plenty of work for magnetic disks. They're right about that, too.

So, naturally then, the question becomes: Exactly how am I to deploy SSDs into my existing storage environment? What is the correct mix of SSD and HDD?

Unfortunately, since you're the top expert on your particular data center, you'll ultimately have to make that call yourself. But fortunately, there are plenty of consultants on hand to give you an idea of what technology works best in any given situation.

Mark Peters, an analyst with the Enterprise Strategy Group, offers some useful guidance in this Q&A with SearchStorage. In it, he explains that fast-paced applications like database acceleration, Web services and financial transactions are probably the primary applications. But his most interesting comments involve location of SSDs within existing infrastructures. If, as he says, SSDs will only gain in speed and capacity, then what does that say about the current need to separate servers from storage, with all the complicated and expensive network infrastructure in between?

Another good read is here on Enterprise Systems. Jon William Toigo, chairman of the Data Management Institute, has a lot to say about the relative cost factors of the various flash technologies out there. But toward the end he points out that SSD values will diminish if they are not deployed correctly. Applications with frequent maximum data loads will wear SSDs out more quickly, leading to higher replacement rates and higher overall costs. So there will likely be instances where DRAM, say, will be preferable to MLC flash, and some cases where the reverse will be true.

Another good approach is to determine which kind of magnetic drive is most suitable for replacement with SSDs. According to InformationWeek's Roger Smith, the prime candidate is a 15k drive that is being short-stroked for high-performance applications like VOD and virtualization. Since you're not getting full value out of the drive's capacity anyway, you'll make out like a bandit swapping three or four with a single SSD.

Ultimately though, and notwithstanding Mark Peters' views on server-embedded storage, deployment decisions will likely fade over time as SSDs are incorporated into integrated storage platforms. A harbinger of this trend is the new Hybrid Storage Pool, in which Sun and Intel have combined flash, DRAM and hard disks into a multi-tiered environment managed by the ZFS file system. The idea is to automate the storage process so data is instantly transferred to the most appropriate medium. Not only does the system cost less than half of traditional arrays on a per GB basis, but it runs on less than a quarter of the energy.

There's a solution to every problem, as the old saying goes. Few people realize that there is usually a problem to every solution. Deployment issues certainly aren't deal-breakers for SSDs, but they hold a lot of sway when it comes to gaining the most from your investment.